1. Field of the Invention
This invention relates to control systems for automatic change-speed transmissions or gearboxes of motor road vehicles, notably heavy commercial vehicles and more particularly motor buses and coaches.
2. Description of the Prior Art
In a first known control device of this kind, a cable and linkage arrangement is adapted to be actuated by means of a lever mounted on the instrument panel of the vehicle and coupled to a selector shaft mounted on the gearbox. However, in actual practice the drivers, especially in the case of a passenger-buses or coaches, experienced some difficulties in operating this type of control device.
In a second known construction the automatic change-speed transmission is controlled through hydro-electronic means comprising essentially an electronic control box coupled on the one hand to the change-speed mechanism or gearbox and on the other hand to a selector keyboard provided with several keys and fitted to the instrument panel within easy reach of the driver's hand.
Now this last-mentioned device is complicated, expensive and a constant source of trouble.